Gas generator



Nov. 28, 1950 H. TOBLER, JR 2,531,657

GAS GENERATOR Filed Feb. 6, 1945 6 Sheets-Sheet l l "5 4 ii iNVENTOR Henry 166(6), Jr.

BY mfs ATTO NEY H. TQBLER, JR

GAS GENERATOR Filed Feb. 6, 1945 6 Sheets-Sheet 2 INVENTOR Hem 706197, I". BY

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ATT'ORNEY Nov. 28, 1950 Flled Feb 6 1945 H. TOBLER, JR

GAS GENERATOR Nov. 28, 1950 6 Sheets-Sheet 5 Filed Feb. 6, 1945 j; Hen

INVENTOR Z5616 J}:

ATTOR Patented Nov. 28, 1950 E STATES r-ATE T oer-ice mesne, assignments, to Allie tlr Erocess- Corporal.- .tion; New. York, N. Y., a corporation of New Yo k Application February 6, 1945; Seriahhlo. 576,488.

3. Qlai ns... (Cl... 23-282) This invention relates to the art of generating gas? by reactionbetween a solid; anda liquid. While the invention arose. out of. the demand. for an-improved means forgenerating gas in-yan emergency, it is not limited to use insuch emergencies. Suchlanrexigency is illustrated .bytne forced landingof. an airplane. in this particular emergency it is desirable. that equipment: benpror vided including a gas generator which maywbe employed to inflate asignai balloonto assist'in locating the position of the forced landing. A generator which is entirely satisfactory under these conditions must meet with. extremely rig? orouscriteria. The; element of time is important, since a balloonfor example must be inflated in a matter of minutes rather than hours, and the fewer the minutes the better. The construction of; the generator itself and the equipment. of ,which it forms a part mustube so simple that there-is no waste of timeyconsumedin the; assembli and operating of more. or less complicated apparatus. The required volume, of gas shouldbe evolvedqvery quickly. Inmany cases the evolution of the gas is the result of an exothermic chemical. reaction, 8.5 for example, the reaction of various hydrides including hydridesof alkali metals and alkaline earth metals with Water. The rapid evolution-of the gas means the liberation; of theheat ofereaction withinaqmatter of minutes. concentrated in a very short time interval; is adequately dissipated, the temperature of th apparatus will rise and become so i hot "that it. cannot be readily handled. It is also desirablethat the evolved gasshould be as free-aspossibleifromentraining liquid, particularly when, ,as is :ottentthe case, that liquid is corrosive in nature. All of these factors and others present inter-related problems to the solution. of which the present invention is directed.

In accordance with this invention, the foregoing factors are correlated and dealt with in a practical manner by providing apparatusin which thegeneration of gas takes place within a container, andunder some pressure, butnevertheless whatmay be termed th ffree generation rate. That is to say, about as rapid generation asean be expected is that at which the gaswould be formed from the. reacting chemicals in open space, and this rate may. therefore be termed the free generation rate. .Such a rate will, obviously, be accompaniedby a tendency ofmhigh temperature rise, as the heatof the'reactionlis liberated in the shortest period of time. {In order to. attain substantially the free. generation rate,

Unless the heat thus liberated and .r

and at. the same time maintain: the solid: charge at. a temperature :below: that at WhiChri t wouldtbe baked or coatedwithsludge, andalso na liberated gas: su fic entl ool t p ve i i nyte the balloon, provision is made for thecontinuons washing of the solid andigtw; for the maintenance ofa.suitable-pressure notgreatly exceedinaha rometric .pnessure; and for-passageways orwduc ts i the generated gas to eiTect,itsremovalvrithout the development ofexcessiye back pressure; It .is accordingly :amobj ect of the present inuens tion to provide a generator having advantages including the following:

I. Simplicitywofconstruction and "operation 2; Portability. and minimum; weight,

"3. Evolutionof aspredeterminedivolume-of.gas rapidly; that is, during a. minimum time period,

4. Evolutionvof 'saidgas in arelatively cook-con;- dition,

5. Evolution of said gas relatively. free from-en.- trained liquid and therefore freeirom entrained by-products which maybe corrosive, e. g., alkalies and alkaline earths 6. Efficiency of gas evolution; 1. a, production of a maximum quantity of gasfrom a minimum weight or volume of solid material; 1

For the sake of'conveniencethe solid body which by reaction with liquid; generates the gas, will be identified generically as the charge. This maybe a salt-lik e hydride, e. g., a hydride of lithium or a hydride ofjan alkalineearth metal, orhydrid'es mad'efrom alloys of lithium anem a; lineearth metals. The invention-isnot however limited to theuse of any particularchemical nor of any particular liquid which'reacts therewith, becausethe inventionres ides in thestructural and functional features which are advantageous in connection witha considerablenumber of spie ciiically different gajs generating chemical actions between solids j and liquids. Those sti tural features can-be employed to advantag connection with the generation or various l including not only hydrogen but also oxyge 'rii"- trogen, hydrogen sulfide, ammonia, hydrocyanic acid andvarious other gases and vapors.

In appreciating, the various features of the invention, itisn'eces sary to bear in mind a '1,- ber of important m atters. The reaction bet een a solidmaterial anda liquid tolfgenerat'e I gas by thatreactioninyolvesia surface reaction and is accompanied. "by the production .of a. .153;-

product. For example, the. reactiOl abettveenla sal -li h r meta en Walther east: ous liquids produces not'only. hydrogenrhutlalso t hvd x le -.t m tal- H awatha 3th by-product may be soluble in the liquid, it tends to form or does form a coating on the hydride particles which retards and may entirely stop the reaction. Now if the particles of the solid reactant are continuously washed by the fresh liquid, fresh surfaces of reactant are continuously presented to the liquid and speed of reaction is thereby facilitated. If a more or less static body of liquid is contacted with the solid reactant, the concentration of by-product builds up and not only is the coating effect just mentioned experienced but also, according to the law of mass action, the reaction is slowed down by accumulation of a product of the reaction. Moreover, heat is frequently generated by the reaction and if the same body of liquid is exposed to the action of the solid reactant, the temperature of that liquid will rapidly increase and the temperature of the evolved gas will be correspondingly high.

On the other hand, if fresh, i. e., unreacted and cool bodies of liquid are continuously brought in contact with the solid reactant and the byproducts, and liquid associated therewith continuously swept away, many of the advantages above listed may be obtained.

The present invention visualizes a lateral spreading out of the charge to a thin depth and contained and maintained within a bell or inverted cup. Now if that shallow inverted cup or dish be placed, while still inverted, in a liquid which reacts with the charge to produce a gas, it will be seen that the reaction is very rapid. Substantially all parts of the charge are immediately accessible to the liquid. The evolved gas must pass downwardly to escape below the depending edges of the dish, bell or cup. Assume that the charge is a salt-like hydride, e. g., lithium hydride and that the liquid is water. The reaction is where AH is the heat of reaction. The gas in passing down through the liquid and then upwardly, heats the liquid and is cooled to an extent depending on the temperature of the liquid. If the charge is maintained within the bell or cup in such manner that there is opportunity for the free movement of gas, and liquid away from the reaction zone, the liquid in the immediate vicinity of the charge is displaced and its place taken by fresh, cool liquid, this action being facilitated by the turbulence produced by the rapid reaction and generation of gas. There is thus a continuous displacement or expulsion of liquid containing by-products and an intake of unreacted and cool liquid, accompanied by a sort of surging motion. Thus the gas is washed and cooled notwithstanding its rapid evolution, indeed that rapid evolution which normally would produce a hot gas in a more or less confined liquid, actually assists in producing a cool liquid.

Moreover, the movement of liquid toward and away from the charge, stale liquid away and fresh unreacted liquid toward the charge has a number of advantages in addition to producing a cool gas. The by-products which may be in the form of sludges, are removed. The surfaces of the reactant particles are Washed and fresh surfaces presented to the reacting liquid. Thus continuity and rapidity of reaction are obtained. Rapidity alone is not enough because even a rapid reaction is ineffective if for any reason it is stopped too soon; and a surface reaction will be stopped too soon or retarded if the surface becomes coated with a material which prevents access of reacting liquid to the surface of the reactant.

The production of a given volume of gas in a minimum time is therefore a function not only of inherent rapidity of reaction but also continuity of reaction. Surface area, i. e., active surface area, or more accurately the ratio of exposed active surface area of the solid reactant to the liquid is also important. The initial surface area may be made large by choosing particles having a selected range of sizes. However, if the surfaces become coated with unreactive sludges or by-products, the effective surface area soon decreases. Hence the necessity of washing the surfaces of the solid particles with the liquid reactant, removing by-products and bringing fresh surfaces of solid reactant into contact with unreacted liquid reactant.

In addition to securing the above mentioned basic operational or method advantages of rapid reaction, continuity of rapid reaction, generation of gas in a cool condition and efliciency of gas production, it is necessary to avoid apparatus features which are awkward or even impractical and in accordance with the invention, the beneficial and advantageous effects are obtained by structures which are compact, simple and portable.

The nature and advantage of the invention will be further apparent from the following further description taken in conjunction with the drawings in which Fig. 1 is a diagrammatic view illustrating certain generic features of the invention;

Figs. 2 to '7 illustrate certain forms of the invention;

Figs. 8, 9 and 10 illustrate a somewhat modified form of the invention;

Fig. 2 is a plan view of the gas generator;

Fig. 3 is a vertical sectional view on the line 3, 3 of Fig. 2;

Fig. 4 is a vertical sectional view on the line 4, 4 of Fig. 2;

Fig. 5 is a perspective view of the charge container;

Fig. 6 is an elevational assembly view of the charge container, balloon and associated parts including a tube or conduit, serving as handle, for conducting the gas from the gas generator to the balloon; I

Fig. 7 is a vertical sectional view showing the said tube or conduit and associated parts including a gas valve;

Fig. 8 is an assembly view analogous to Fig. 6;

Fig. 9 is a sectional view on line 9, 9 of Fig. 8 and Fig. 10 is a perspective view of the gas generator with parts broken away.

Referring first more particularly to Figs. 1 to 5 inclusive the apparatus has a generally rectangular shape. This however is a matter of choice or manufacturing convenience and the apparatus may have any desired geometrical shape, for example, it may be cylindrical or hexagonal. The particular form of apparatus shown in the drawings for purposes of illustration includes a rectangular inverted cup or bell having a closed top I, side portions 2a, end portions 2 and land a bottom 5. The charge container is positioned within an outer shell having an open bottom portion Ba, a top 6 and side or skirt portions 1. The top 6 is closed except for an opening l3 which receives a tube or handle 8 connected thereto which serves to lead the generated gas from the generator to a place of disposal. The sides 2a and ends 2 and 4 of the charge container may be in spaced relation to the shell 7. As shown in the drawing, however, the sides 2a have a close fit with the corresponding skirt portions of the shell so that the charge container is spaced from the shell only at the ends thereof as clearly shown in Figs. 1, 3 and 4. Whatever may be the particular spacing arrangements of the vertical side walls of the charge container, in relation to the opposed shell walls, at least a part of said container side walls should be spaced from opposed side walls of the shell. The charge container may be supported within the shell in any convenient manner, as for example, by means of plates H secured tothe walls of the shell and having brackets [2 on which the charge container is supported.

Instead of reducing the depth of the charge to such a small dimension that, for a given weight or volume of charge, the lateral cross sectional area of the charge and consequently the lateral dimensions of the apparatus as a whole, would be extended to such an extent as to make the apparatus awkward or impractical to manipulate and transport, the beneficial eilects which have been described above may also be obtained by restricting the lateral cross sectional area of the charge and the apparatus and by increasing the depth of the charge while at the same time rendering the charge readily accessible to liquid, as for example, by means of a reticulated or perforated structure of the charge container. For example, as illustrated in Figs. 1, 3 and i the ends of the charge container in spaced relation to the walls I of the shell have solid or imperforate portions 2 depending from the top I and also perforated portions 4 extending up from the bottom 5 to the imperforate end portions 2. The bottom 5 is also perforated or reticulated.

It will be understood that in assembling the apparatus the charge container is filled with a suitable gas-generating solid material which may be in general any solid material which generates gas upon contact with liquid. It may be, for example, a salt-like metallic hydride having in a typical case a particle size varying for example from about A; to inches. Lithium hydride may be taken as a specific illustrative example. Such material when properly prepared is inherently very reactive with water with the production of hydrogen gas and lithium hydroxide as a lay-product. reaction, as for example, in the case of sea water, the reaction is even more rapid than in the case of fresh water owing to the action of the acid of the water with the lithium hydroxide byproduct. In using the apparatus it may be im- Inersed in a liquid which reacts with the solid to produce gas after connecting to a gas collector or balloon as hereinafter more specifically described, so that the top 6 of the outer shell is approximately level with the surface of the liquid. Owing to the rapid evolution of gas and the development of back pressure in the balloon, the level of water within the shell is depressed so that it may be for example approximately at the point 3 shown in Fig. 1 which is about midway between the top I of the charge container and the bottom of the imperforate end walls 2. 1t is to be understood that owing. to the vigorous reaction and development and evolution of gas and surging of water into andout of the charge container and shell, the hydrostatic. level men- When the water has an acid.

tioned is not static but constantly fluct'uatingt Gas developed within the charge container must necessarily pass downwardly because the top I is closed and the endportions 2 imperforater These end portions form a seal which compels the gas to pass through the waterbetween the end portions 2 and the opposed walls 7 or the shell. As the reaction progresses and pressure in the balloon increases, thus tending to further depress the water level, within the shell, it may be desirable to further immerse the generator in the waterto assist in overcoming this back pressure and in maintaining said seal.

In some cases it is possible to carry the perforated portions. 4 all the way upto thetop l and in some cases the side walls or the charge container, including those spaced from the shell, e. g., the walls 2, may be solid or imperforate all the way down to the bottom of said charge container. It has however been found preferably or highly desirable tohave imperforate parts 2, for example, in addition to the perforated portions 4.

The vertical dimension of the imperforate or solid side walls of the charge container (which walls are spaced from the shell) e. g., the walls 2 of Figs. 1 to 5, has been found to be important especially where the chemical reaction which generates the gas is an exothermic one. When the dimension is too large, it has been found that r there is inadequate washing of all parts of the charge with liquid with the result that in the upper part of the charge the particles become coated with a by-product of the reaction, e. g., a metallic hydroxide in the case of salt-likehydrides (such a lithium hydride, potassium hydride, calcium hydride, etc.). This coating prevents or greatly retards reaction, the more so as the coating becomes hardened by the heat evolved, and the efficiency and capacity of: the

- generatoris impaired.

When the dimension is too small, the gas escaping from the charge container is incompletely washed and the gas temperature correspondingly higher. A range of three quarters of an inch to one and one quarter inches (%-I% is recommended in dealing with hydrides of the nature of lithium hydride. found satisfactory. The length of the perforated portions 4 may be approximately equal to those of the imperforate portions. These dimensions are indicated as DI and D2.

As above mentioned a condition of more or less turbulence exists within the charge container. The rapid evolution of gascauses the expulsion of liquid within the container accompanied by the lay-products of the reaction, as for example, lithium hydroxide sludge in the case of lithium hy dride. This water, including that which has reacted with the lithium hydride is of course more or less warm o hot as a result of the reaction. When expelled or forced out through the perforations, its place is taken by cool water. There is thus a surging of water into and out of the charge container accompanied by a constant washing or bathing of the surfaces ofthe particles of solid material. The by-pro'duct hydroxide which in the absence of such washing would accumulate on the surfaces or said material and also clog the free spaces between said particles, is continuously removed. Thus, fresh surfaces of the active solid material are continually brought into contact with unreacted cool liquid and rapidity and continuity of reaction is ensured with the evolution of gas in a relatively cool con' dltion. It is desirable toavoid any filling up of One inch has been the free spaces between the particles so as to maintain a sufiicient minimum free space to permit the free passage of gas and liquid out of the charge container and unreacted liquid into the said container. Any clogging or filling up of these spaces would tend to confine the gas within the container and the back pressure thus developed Would force the liquid away from the particles and tend to bring the reaction to an end. It will be noted that the turbulence and washing action which has been described are effective in providing for the free passage of gas and liquid and in providing continuity as well as rapidity of gas evolution.

Provision is also made for permitting the generated gas to pass freely to the balloon without any undue restrictions in its path which would tend to raise the velocity too high, generate too high a back pressure in the charge container and also carry entrained liquid into the gas collector. The free space or area between the ends 2 of the charge container and the opposed walls 7 of the shell is therefore preferably made sufiicient to guard against undue pressure drop and undue velocity of the gas. As an indication of a desirable condition, it may be recommended that this free space or area be chosen so that the gas velocity will not exceed about 150 feet per minute or about 2.5 feet per second. In the drawings the space between the end Walls 2, Q of the charge container and the opposed walls 1 of the shell is indicated by D3.

he space between top 1 of the charge container and the top wall it of the shell acts as a settling or separation chamber in order to remove particles of liquid from the gas so that the latter when delivered to the balloon may be in as dry a condition as possible. Here again it is recommended that this space be chosen so that velocity of gas therethrough does not exceed about 150 feet per minute or 2.5 feet per second. The vertical dimension of this space is indicated in the drawing by the symbol D4, and about 1 inch has been found satisfactory with generators having a maximum capacity of about 4; cubic feet of gas per minute. The distance D may advantageously be increased to decrease the velocity of gas therethrough below 150 feet per minute since the less the velocity, the better the separation of liquid.

To guard against the escape of gas, the skirt or side walls of the shell are preferably carried down a reasonable distance below the bottom 5 of the charge container.

The diameter of the tube is also preferably controlled so as to prevent an undue pressure drop and further provide for the free passage of gas from the generator into the balloon and thereby further guard against t-e development of back pressure in the charge container which would tend to force liquid away from the solid material and interfere with continuity of the reaction. With a I. D. tube a velocity of 660 F. P. M. is satisfactory, while for a l" I. D. tube a velocity of 744 F. P. M. is satisfactory.

Coming now to the more specific structural details, the top and bottom walls 5 and H of the shell "in may be secured to the side walls '5 thereof at the joints or shoulder portions 21 and i6. Referring to Fig. 4, the connection at 25 is permanent, while the bottom cover ii is removable so that in operation the bottom of the shell may be entirely open for the free passage of liquid into and out of the charge container. The perforated portion of the end walls 4 of the latter may be double walled as shown in Figs. 3', 4 and 5 comprising an inner perforated portion connected to an outer perforated portion at the joints 25. The bottom of the charge container may likewise be double walled as shown, the inner bottom wall being connected to the inner side walls at the joints 66 and the outer bottom wall being connected to the outer side walls at the joints 2. The purpose of the double walled structure is to aid in the cooling action of the liquid on the gas by slowing down somewhat the velocity of the gas passing out of the charge container while still maintaining free passage of gas and liquid into and out of said container.

Reference will now be made to the details of the structure for conducting gas from the generator to the balloon and the valve structure in the latter. This comprises the tube 8 having an annular shoulder or flange i=3 near the bottom thereof which receives an annular raised lip 9 defining an opening [3 in the top 6 of the shell. The tube 8 is provided with a pin 59 extending diametrically across the tube 8 and secured thereto at the ends of said pin and cooperating with slot 3'! in tube or sleeve 35 to form a bayonet joint. Within tube 8 there is a tube Gil provided with slot :58 through which said pin 4s extends. A gasket 54 is provided. The tube 55% has a smaller diameter than the tube 3 and the pin 49 prevents the tube 6E from falling out prior to the time when the tube 8 is connected to the gas generator.

The tube 13 carries at the top thereof detachable sleeve 45, the connection between tubes 8 and 45 comprising the flange 35 and gasket 41. The top edges of the tube 45 serve as the valve seat 53 for the valve 52 which is a solid hemispherical resilient body, as for example, rubber, normally held in closed position on the valve seat by resilient or rubber bands 14 passing over the top of the valve and secured. to the tube 45 by means of the lashing 5 The nipple or neck 4] of the balloon is also secured to the tube 45 by lashings 55 and 56. An extension of lashing 56 provides cord 5i to which cap 58 is attached to the end of tube d5 when the balloon is filled and tube 55 disconnected from tube 8.

The tube is perforated so as to maintain as far as possible the eifective internal cross section of tube 8 and normally occupies a lower position than that shown in Fig. 7 and is brought into the raised position shown in that figure by the engagement of the bottom edges of said tube 60 with a pin 22 extending across the opening l3 defined by the annular lip 8 on the top of the shell 6.

In using the apparatus the tube 8 and its associated parts including the balloon 4a as shown in Fig. 7 are inserted through the opening l3 in the top of the shell until the flange l9 engages the gasket [4 on the lip 9. In this operation, the bayonet joint slot 55 on the tube 8, engages the locking pin 22, by rotation of the tube 8, thus securing the tube 8 to the shell of the generator. At the same time the vertically movable perforated tube so is raised into the position shown in Fig. 7 by engagement with said pin 22 thereupon raising or opening the valve 32. At the same time the seal cap 2'! is removed from its sealing connection with the gasket 2&0 provided on flange 25a of the bushing 26 and drops to the top of the shell as shown in Fig. 3. It will be understood that the purpose of the seal cap 21 as well as the removable bottom cover I! is to prevent access of moisture, to the interior of the shell and charge therewithin until the apparatus is in condition for use.

The way in which the seal cap 27 is automatically removed when the tube 9 is secured in place as above described, and the structure involved is as follows: The lip or flange 9 has a lower extrusion or bushing 26 carrying a flange 26a brazed or otherwise joined to the top 6 of the shell. To said bushing 29 are secured two diametrically opposite ears 26b, defining with the lower edges of said bushing 26 slots 29 which receive pin 21a on the seal cap and by means of which the said cap is normally held in sealing connection with the said bushing 26. The cap 2'! also is provided with lugs 29a for use in initially mounting the cap on the bushing 26 in assembling the apparatus. When the tube 8 is inserted in the opening 13 and connection made by engagement of pin 22 in the slots to make a bayonet joint by rotation of tube 8, the edges 8a of the tube 8 engage the pin 2111 on the seal cap thus twisting the latter and this combined with the downward movement of the tube 8 removes said cap which then falls on the top of the charge container.

The tube 8 is provided with a grip 33 rotatably mounted thereon and reel 32 fixedly secured to tube 8 mooring line 34 of which is secured to swivel joint 34a. Lashing 56 is extended to form loop 59 which is also secured to swivel joint 34a.

The apparatus shown in Figs. 8, 9 and differs from that in Figs. 2 to 7 in detail. The bottom cover ll (see Fig. 8) is similar to that shown in Fig. 3 and is sealed to the shell 1a by means of a tear strip 83 removable by means of key 85 along score lines 92 and 92a. The sealing structure at the top of Figs. 6 and 9 differs from that shown in Fig. 3 because the tube 8 is not only secured to the top 6 of the shell but is also recessed within a removable cover 8! normally sealed to the shell by a tear strip 82, removable by means of key 84 along the score lines 86 and The space between the top 6 of the shell and the cover 2! and the side walls 99, 89 serves as storage space for the balloon and the valve attachments thereof. In the structure shown in Figs. 8, 9 and 10, therefore, all the equipment may be contained within a single package, whereas in the equipment illustrated in Figs. 2 to 7, the balloon and its associated equipment, including the tube 8 and so forth, must be stored in a package separate from the generator.

In Figs. 8, 9 and 10, the tube 8 has mounted thereon a reel 92 which carries the balloon mooring line To the tube 8 is riveted by rivets 79 an annular flange or shoulder is carrying a gasket 77. The balloon nipple is secured by lashings 95 and 96 to a bushing 19 which carries the valve mechanism, this bushing having a valve body portion 7| carrying a valve seat 43. The valve i6 is provided with valve orifices 9|], the valve plate if; being normally held against the gasket 6! on seat 413 by spring 14 secured to a spring holder 9i which in turn is secured to the bushing it by means of bracket 79. The lower part of the valve body H carries a transverse locking pin l2 which cooperates with bayonet joint 69 to connect the bushing E9 to the tube 9. The connection is effected by fitting the valve body Fl over the tube 8 and locking it in place by means of the pin l2 and the bayonet joint 69. The bottom cover ii is of course removed for the purposes previously described.

The lashing 86 is extended to form the loop 59 attached to snap fastener es secured to swivel joint 9 3a which in turn is secured to mooring line 36. Line El which is also an extension of lashing 96 is secured to stopper 93 which may be inserted in valve bod it after the balloon is inflated.

What is claimed is:

1. A portable apparatus for generating and supplying gas for inflation of signal balloons and the like, comprising an outer shell, a removable bottom for said shell, whereby the apparatus may be readily immersed in water when such bottom is removed, the top wall of said shell being provided with a gas escape opening, a charge container mounted in said outer shell and spaced from the top, side and end walls thereof, said charge container having a perforated bottom and having end walls, the lower portions of which are perforated while the upper portions of said end walls are unperforated, a detachable closure for said gas escape opening in the top of said outer shell, a gas escape tube, coupling means for coupling said gas escape tube to said gas escape opening, said gas escape tube being movable downwardly to engage said closure to detach it from the gas escape opening.

2. The combination as claimed in claim 1, wherein the coupling means for attaching the gas escape tube to the gas escape opening is of the bayonet slot type.

3. The combination as claimed in claim 1, wherein the perforated bottom and perforated side walls are made double, comprising inner and outer perforated members arranged parallel and close together.

HENRY TOBLER, JR,-

BEFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 515,500 Nobel Feb. 27, 1894 726,139 Busch Apr. 21, 1903 834,831 Margreth Oct. 30, 1906 978,641 Poe Dec. 13, 1910 1,016,681 Fallot Feb. 6, 1912 1,029,692 Kirkwood June 18, 1912 1,537,519 Yablick May 12, 1925 1,684,979 Valentour Sept. 18, 1928 2,211,430 Ness Aug. 13, 1940 FOREIGN PATENTS Number Country Date 718 Austria Dec. 27, 1899 32,626 France Oct. 4, 1927 

